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arXiv · 1906.10867

Conclusive nonlinear phase sensitivity limit for a Mach-Zehnder interferometer with single-mode non-vacuum inputs

Jian-Dong Zhang·Zi-Jing Zhang·Jun-Yan Hu·Long-Zhu Cen·Yi-Fei Sun·Chen-Fei Jin·Yuan Zhao
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Abstract

Many works have stated that nonlinear interactions can improve phase sensitivity beyond the Heisenberg limit scaling of $1/N$ with $N$ being the mean photon number. This raises some open questions---among them the conclusive sensitivity limits with respect to single-mode inputs. Namely, when one of two inputs is vacuum, is there a shot-noise-style sensitivity bound on a nonlinear Mach-Zehnder interferometer? Within the reach of second-order nonlinear phase shifts, we make an attempt to provide an answer to this question. Based upon phase-averaging approach, this puzzle is partially resolved with careful calculations of the quantum Fisher information regarding three kinds of common inputs: Gaussian states, squeezed number states, and Schr\"odinger cat states. The results suggest that shot-noise-style sensitivity limit is no longer available, and the ideal candidate is squeezed vacuum.

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Jian-Dong Zhang, Zi-Jing Zhang, Jun-Yan Hu, Long-Zhu Cen, Yi-Fei Sun, Chen-Fei Jin, Yuan Zhao. 2019-06-26. Conclusive nonlinear phase sensitivity limit for a Mach-Zehnder interferometer with single-mode non-vacuum inputs. https://arxiv.org/abs/1906.10867

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